Error de sintaxis YAML: no se permiten caracteres de control en la línea 1, columna 1

I see you solved this already, but in my experience weird control characters at the beginning of a file usually result from editing in some GUI editor that likes to add the byte-order mark to text files. They could be invisible, but when you run some tool like hexdump -C on them, you see the extra bytes:

00000000  ef bb bf 73 6f 6d 65 20  74 65 78 74 20 68 65 72  |...some text her|
00000010  65 0a                                             |e.|
00000012